This invention relates to faucets and is particularly concerned with electronically-controlled faucets having a cartridge-type mixing valve for setting water temperature mounted in a housing. Hot and cold water is supplied to the mixing valve. A discharge line extends from the housing to the spout. A user sets the mixing valve, through either mechanical or electronic actuators, to obtain a desired water temperature. Typically a solenoid-actuated pilot valve in the discharge line turns the water flow on and off. Proximity sensors control the pilot valve.
The pilot valves used in faucets of the type described are somewhat intolerant of foreign matter in the water. Accordingly, it is common to use a filter or screen to remove foreign particles upstream of the pilot valve. Preferably filtering would be done immediately before water enters the pilot valve but this is not a convenient location in terms of installing and servicing the filter. For purposes of aesthetics and mechanical protection, the pilot valve is always located beneath or behind a faucet housing, wall, sink or the like. Thus, if the filter is located adjacent the pilot valve, the filter is relatively inaccessible and certainly inconvenient for routine maintenance. But placing the filter remote from the pilot valve limits the effectiveness of the filtering.
The useful life of known filters has been limited by their cross-sectional area. Filters are provided in the water lines and therefore they are restricted by the cross-sectional area of the line. This means the filters are subject to clogging, which either restricts flow or reduces the filter's effectiveness at removing impurities.
Another problem with this type of faucet is the need to prevent cross flow between the hot and cold water lines. Check valves (also known as back checks) in the hot and cold water lines can prevent cross flow but again the mounting of such devices poses a problem. Placing the check valves in the supply lines themselves means the lines have to be disconnected for servicing or replacement. This increases the potential for leaks once the check valves have been serviced or replaced